IBRION

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IBRION = -1 | 0 | 1 | 2 | 3 | 5 | 6 | 7 | 8 | 44 

Default: IBRION = -1 for NSW=−1 or 0
= 0 else

Description: IBRION determines how the ions are updated and moved.


For IBRION=0, a molecular dynamics is performed, whereas all other algorithms are destined for relaxations into a local energy minimum. For difficult relaxation problems it is recommended to use the conjugate gradient algorithm (IBRION=2), which presently possesses the most reliable backup routines. Damped molecular dynamics (IBRION=3) are often useful when starting from very bad initial guesses. Close to the local minimum the RMM-DIIS (IBRION=1) is usually the best choice. IBRION=5 and IBRION=6 are using finite differences to determine the second derivatives (Hessian matrix and phonon frequencies), whereas IBRION=7 and IBRION=8 use density functional perturbation theory to calculate the derivatives.

  • IBRION=-1
  • IBRION=0: molecular dynamics.
  • IBRION=1: ionic relaxation (RMM-DIIS).
  • IBRION=2: ionic relaxation (conjugate gradient algorithm).
  • IBRION=3: ionic relaxation (damped molecular dynamics).
  • IBRION=5 and 6: second derivatives, Hessian matrix and phonon frequencies (finite differences).
  • IBRION=7 and 8: second derivatives, Hessian matrix and phonon frequencies (perturbation theory).
  • IBRION=44

Related Tags and Sections

NSW, SMASS


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